Listening to speech is more effortful for people with hearing loss than for those with normal hearing. Individuals with hearing loss report greater amounts of fatigue, anxiety, and more sick-leave from work, and social isolation. All of these factors impact quality of life for individuals, their friends and families. This project is designed to better understand what makes speech perception more effortful than what would predicted by common audiological measures like pure-tone thresholds and speech intelligibility scores. Specifically, we will explore the mental cost of relying on context to figure out words, and whether that process gets disrupted by the need to continue listening to upcoming sentences. We will also explore whether slower speaking rate allows listeners to recover from mistakes in a timely fashion without missing the next sentence. These studies will start with people who use cochlear implants, which are neural prosthetic devices that give auditory sensation to people who have severe to profound hearing loss. We will quantify listening effort using time- series measures of pupil dilation. These studies are intended to help understand listening effort and the experience of hearing loss in ways that have not yet been revealed. After identifying particularly problematic listening situations, we will expand the scope of work to include people with mild to moderate hearing loss in similar experimental conditions.